This research project is concerned with a system approach to the management of critically ill patients in a clinical setting. Particularly interesting and important problems involve cardiovascular disorders that give rise to low output syndrome. Effective therapy principally involves the administration of one or more fluids and/or drugs in a critical care unit environment. In order to accomplish the goal of developing systems capable of assisting in the medical management of a critically ill patient on a closed-loop basis, it will be necessary to develop validated models. A state variable approach is utilized in the mathematical modeling of pertinent pharmacokinetic and physiologic processes. This includes three principal subsystems: Pharmacokinetics, Drug/Receptor Interactions, and Cardiovascular Dynamics. Program output includes recommendations for therapy as well as predicted pre- and post-intervention physiologic data values.